1. Field of the Invention
The present invention relates to face masks in general and more particularly to a face mask that is stress deformable to seal the mask against a wearer's face.
2. Discussion of the Related Art
Filtering face masks are worn by individuals who desire to filter the air they breathe, either inhaled to filter out particulates in the ambient air or to filter exhaled air, such as required by medical professionals during the treatment of patients. The mask can be of a planar configuration or of a unidirectional folding configuration. Other configurations include those having shaped bodies including cup types or duck-billed types.
A planar type mask does not employ any measures to seal the mask against the wearer's face. Therefore, when worn, this type of mask leaves large gaps between the mask and the sides of the bridge of the nose of the wearer. This results in a large quantity of the unfiltered air being inhaled as entering through these gaps, thereby defeating the purpose of wearing the mask. Since the majority of the mask is in direct contact with the wearer's skin, the mask does not form a breathing space for the wearer and does not effectively filter the air.
Unidirectional folding masks also have inherent disadvantages. Although the unidirectionally folded mask can be spread out in a longitudinal direction, this configuration has its own disadvantages. A folded portion of the unidirectionally folded mask tends to cling on a sensitive portion of the wearer's face such as the tip of the wearer's nose or the wearer's lips, thus resulting in discomfort for the wearer.
Some masks, such as unidirectionally folded masks or duck-billed masks, incorporate metal wires or aluminum strips in the design. The wires and strips are adapted to function as a nose clip seal to eliminate or minimize the gap between the wearer's skin and mask in the bridge area of the wearer's nose. However, these sealing features are easily deformable and are thus easily pulled straight. Therefore, even minimal pulling forces on the mask tend to undo the seal around the bridge of the wearer's nose.
The cup type mask generally employs a hard cup type shell which cannot be folded and is therefore inconvenient to carry and is not widely accepted. Further, the cup type mask employs a wider aluminum strip to act as the nose clip seal. However, the larger aluminum strip utilized for the seal exhibits an increased rigidity such that the strip cannot be completely enjoined against the bridge of the wearer's nose to create a proper seal. To resolve this problem, the cup type mask generally uses straps having a greater pull force to keep the mask in a sealing interface with the wearer's nose by increasing the pressure applied by the mask against the wearer's face. However, prolonged wearing of this mask with increased pressure results in pain to the wearer and a deep skin indentation.
The cup type mask also has a relatively large interior cavity which, when the wearer breathes, primarily causes an exchange of air within the cavity rather than drawing air through the mask. This results in a low concentration of oxygen and increased moisture inside the mask, thereby causing the wearer to experience suffocation and a moist feeling. In some cases, the wearer can also experience cases of eczema.
Although a variable plane cavity type mask is relatively easy to use, it does have problems. Manufacturing of this mask requires forming protuberant rings on each end of the mask and at the center of a sealing strip disposed on an upper edge of the mask. While the rings are merely fabricated by a plastic molding process, a fixing strap must then be affixed in an overlapping insertion manner. This results in a relatively complicated manufacturing process for this mask with correspondingly high costs. Additionally, the two ends of the fixing strap on the bottom edge of the mask are respectively fixed in a section of the mask through which the strap passes. The ends of the fixing strap are fixed first and then the strap is packed which results in decreased manufacturing efficiency. Finally, the ends of the upper and lower fixing straps are all fixed on the sealing strip and in the upper and lower sections, so the length of the straps is not adjustable to accommodate the different sizes of heads wearing the masks.
Therefore, previous masks often offer either ease of manufacturing with a corresponding beneficially low cost, but do not seal about the user's face, or, the masks provide a desired level of sealing, but are relatively complicated to manufacture with a correspondingly undesirable high cost.
Thus what is desired is a mask that is uncomplicated and inexpensive to manufacture and yet provides sealing between the mask periphery and the user's face.